1. Technical Field
The present invention generally relates to the suppression of motion sickness in human operators viewing display devices.
2. Description of the Related Art
Motion sickness is provoked by sensory conflict between visual and sensory-motor activities that involve the vestibular system through head movements. Associated with motion sickness is a constellation of autonomic symptoms such as pallor, drowsiness, salivation, sweating, nausea and, in more severe cases, vomiting. Although some individuals eventually adapt to situations that initially provoke such sickness, others do not. In these individuals, occurrences may be severe enough to arrest task performance until the symptoms subside.
In field experiments conducted by the U.S. Army Research Laboratory on indirect vision driving, some symptoms of motion sickness occurred in most of the participants. As shown in FIG. 1, participants, such as operator 10, drove a ground vehicle 11, while viewing a vehicle-mounted display 12. The display provided the participants with images of the external scene return from a forward-looking camera 14 mounted on the exterior of the vehicle. The cab area 16 was completely enclosed to prevent direct viewing of the external scene by the participants. On average, one out of eight participants was made sick enough to abort the driving task.
In other experiments, participants have reported symptoms of motion sickness while operating a movable camera, e.g., a camera mounted on a remote vehicle, from inside a moving control vehicle. Symptoms of motion sickness can be particularly strong when the control vehicle is turning in a direction opposite to the direction of turn of the camera. In such a case, the motion of the scene viewed on the display is directly opposite to that sensed by the vestibular system of the human operator riding in the control vehicle.
With respect to the example previously provided in FIG. 1, if the vehicle 11 is turning as indicated by arrow A and the camera 14 is simultaneously rotated clockwise at a rate of turn greater than that of the vehicle (arrow B), the sequential images of the exterior scene displayed to the user are as shown in FIGS. 2A and 2B. That is, the image 20 associated with the exterior scene, e.g., the sign 18, is displayed to the operator as moving to the left across the display device 12. Since an operator is accustomed to an exterior scene moving to the right when the vehicle in which the operator is located is turning to the left, motion sickness can be induced in the operator.